I have a single knob push/pull type shower valve. My question is, when I pull out the knob to fill the tub, the valve closes like normal but when I pull the diverter to allow the shower to run, the valve pulls out fine but is really hard to push back in. I have two of the same valves installed, one in the master and one in the guest bathroom. I took the cartridge out of the bathroom that works fine and tried it in the other bathroom but still had the same problem. Any suggestions what could be causing this or how I can fix it?